Test fixes and improvements.

Remove redundant -fno-stack-protector run with openbsd.
Add -target to the -fstack-protector tests so they pass on openbsd.

Patch by Brad Smith.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@209991 91177308-0d34-0410-b5e6-96231b3b80d8